Tachycardia & Potassium Deficiency

by Ruth Coleman

About Ruth Coleman

Based in North Carolina, Ruth Coleman has written articles and manuals for more than 25 years. Her writing has appeared in community newspapers and places of employment. Coleman holds a Bachelor of Science in biology from Salem College, a Doctor of Medicine from Ross University and is the recipient of numerous academic awards.

Potassium is an electrolyte, or a mineral in the body that has an electric charge. When the potassium in the bloodstream reaches the kidneys, they reabsorb most of this mineral, trying to keep as much as possible in the bloodstream, available for use. The kidneys will try to excrete some potassium, however, if the level gets too high, which helps protect against some of the effects of high potassium on heart rate.

Potassium Deficiency

The potassium levels in the bloodstream should normally range from 3.5 mEq/L to 5.0 mEq/L. The medical term for an abnormally low level of potassium, or a level less than 3.5 mEq/L, is hypokalemia. People can develop a potassium deficiency as a result of several conditions, as explained in “Current Medical Diagnosis & Treatment” by Dr. Kerry Cho, assistant clinical professor of medicine at the University of California. It can be the result of long-term laxative abuse, due to diuretics, diarrhea, vomiting, dehydration, an adrenal gland disorder, certain tumors or a kidney disorder.

Symptoms of a Potassium Deficiency

The symptoms depend upon how much of a deficiency it is. People usually do not have any symptoms at all unless their potassium level is less than 3.0 mEq/L, Dr. Gary Singer, assistant professor of clinical medicine at the Washington University School of Medicine, explains in “Harrison’s Principles of Internal Medicine.” At that level a person can have weak muscles and muscle aches, and may also feel tired. If the potassium level falls even lower, the respiratory muscles can be affected and become weak, which can result in paralysis. The patient may also have problems with her heart.

The Heart and a Potassium Deficiency

People who have a low level of potassium will have an EKG, or an electrocardiogram, writes Dr. James Lewis III in “The Merck Manual for Healthcare Professionals.” An EKG will show the rhythm of the heart, the heart rate and any abnormality in its electrical activity. Hypokalemia usually does not have much of an effect on the heart unless the potassium level is below 3.0 mEq/L. Then the heart may contract too soon, there may be a problem sending signals within the heart, and the heart may beat too fast.

Tachycardia and a Potassium Deficiency

The heart normally beats 60 to 100 times every minute. Bradycardia describes a heart rate that is slower than 60 times a minute, while tachycardia is the medical term for a heart rate that beats faster than 100 times every minute. As explained in “The Merck Manual for Healthcare Professionals,” if the potassium deficiency is less than 3.0 mEq/L, people can develop tachycardia. Sometimes, the heart may not just beat fast, but develop a fast, irregular rhythm that will only get worse as the potassium levels decrease. If this continues, the affected person can develop a fast heart rate and fatal rhythm.